Umbrella base



FIG. 1 is a top perspective view of an umbrella base showing our new design;

FIG. 2 is a left side elevational view thereof, the right side and front and rear being a mirror image; and,

FIG. 3 is a top plan view thereof.

The broken lines shown in FIGS. 1–3 are for illustrative purposes only, and form no part of our claimed design. The bottom of the umbrella base is unornamented and forms no part of our design. 

The ornamental design for an umbrella base, as shown and described. 